Anatomy: Segisaurus was a lightly-built, bird-like theropod dinosaur. It had a long flexible neck, long head, three-toed feet, a short body, a long tail, hollow bones, long, strong legs, arms with long forearms and long, clawed fingers. Its collar bone was similar to that of a bird (this characteristic is unusual for dinosaurs and may indicate a close link to birds). Segisaurus was roughly 3 ft (1 m) long as a sub-adult (it is known from only a parital skull).

Diet: Segisaurus was a carnivore (meat-eater); it ate small animals, like insects.

Fossils: A partial skull of a sub-adult was found in Arizona, USA. Segisaurus was named by Charles L. Camp in 1936. The type species is S. halli.